Integrated heat spreader with mechanical interlock designs

ABSTRACT

An integrated heat spreader is presented. The heat spreader is constructed and arranged to be adhesively affixed, with a sealant, to at least a portion of a component, such as a substrate. The heat spreader includes a body portion, a lip portion substantially vertically oriented and integrally formed with the body portion, and a step portion integrally formed with the lip portion. As such, adhesion of the heat spreader to the sealant is increased, and failure due to shear stresses at the heat spreader bonding surface is prevented.

BACKGROUND

[0001] 1. Field

[0002] This invention relates generally to packaging for integratedcircuits. More specifically, this invention relates to a novelintegrated heat spreader.

[0003] 2. Background and Related Art

[0004] Integrated circuits generate heat to varying degrees. In typicalapplications, such radiated heat must be dissipated to ensure thatthermal effects do not impair the performance of, or even damage,integrated circuits. With increasing demands in computing speeds andmemory, heat removal has become a critical focus area in packaging.Various techniques have been employed to dissipate radiated heateffectively, including the attachment of integrated heat spreaders(heatsinks) or fans to integrated circuits.

[0005]FIG. 1 (Prior Art) illustrates portions of an electronic package100. Package 100 includes a die 110, a substrate 120, and pins 130. Anintegrated heat spreader 101 is adhesively attached to substrate 120 viaa sealant. Heat spreader 101 absorbs heat radiated by die 110 andsubstrate 120.

[0006]FIG. 2 (Prior Art) illustrates a portion of another electronicpackage 200. Package 200 includes a die 210, a substrate 220, and pins130. Heat spreader 201 is attached to substrate 220 via an adhesive bond240. Heat spreader 201 is in contact with die 210 to absorb radiatedheat of die 210. Heat spreader 201 includes lips 250 that extend fromthe heat spreader and adhere, via adhesive bond 240, to substrate 220.In package 200, one face of each lip 250 is in contact with adhesivebond 240.

[0007] The splitting or separating of a laminate into layers is known asdelamination. In particular, heat spreader-to-sealant delamination inelectronic packages may lead to the popping off of heat spreaders fromthe integrated circuits to which they are attached. For instance, heatspreader 201 may pop off of substrate 220, causing package 200 to fail.Moreover, high combined shear and tensional stress distributions areoften exhibited by packages with off-center dies. Because of severeshear stress (torsional) distributions, heat spreader-to-sealantinterfacial delamination may occur. Heat spreader-to-sealant adhesionmay be unable to withstand the high shear stresses generated at the heatspreader-to-sealant interface.

[0008] Therefore, what is needed is an improved integrated heatspreader.

BRIEF DESCRIPTION OF THE DRAWINGS

[0009]FIG. 1 (Prior Art) illustrates portions of an electronic package.

[0010]FIG. 2 (Prior Art) illustrates portions of an electronic package.

[0011]FIGS. 3A and 3B are plan and side views, respectively, of anintegrated heat spreader according to an embodiment of the presentinvention.

[0012]FIGS. 4A and 4B are plan and side views, respectively, of anintegrated heat spreader according to an embodiment of the presentinvention.

[0013]FIGS. 5A and 5B are plan and side views, respectively, of anintegrated heat spreader according to an embodiment of the presentinvention.

[0014]FIGS. 6A and 6B are plan and side views, respectively, of anintegrated heat spreader according to an embodiment of the presentinvention.

DETAILED DESCRIPTION

[0015] An integrated heat spreader, as presented herein, is constructedand arranged to be adhesively affixed, with a sealant, to at least aportion of a component, such as a substrate. The heat spreader includesa body portion, a lip portion substantially vertically oriented andintegrally formed with the body portion, and a step portion integrallyformed with the lip portion. As such, adhesion of the heat spreader tothe sealant is increased, and failure due to shear stresses at the heatspreader bonding surface is prevented.

[0016]FIGS. 3A and 3B are plan and side views, respectively, of anintegrated heat spreader 300 according to an embodiment of the presentinvention. Heat spreader 300 includes a heat spreader element 301. Heatspreader element 301 may be shaped to suit a particular application. Forinstance, heat spreader element 301 may be rectangular or square. Lips310 extend substantially vertically from heat spreader element 301. Astep 320 extends from each lip 310 and may be regularly or irregularlyshaped. In the embodiment of FIGS. 3A and 3B, steps 320 are rectangularand extend laterally from lips 310 in a substantially perpendicularmanner.

[0017] Heat spreader element 301, lips 310, and steps 320 may berespectively formed of the same materials or different materials.Exemplary materials include copper, copper with a nickel or othercoating, aluminum, a carbon/carbon composite, or a carbon/metalcomposite. Exemplary carbon/metal composites include carbon/copper andmatrix fiber reinforced composites. Heat spreader 300 may be selectivelyplated or plated over its entire surface area. Exemplary electrolyticplating materials include gold, silver, tin, nickel, and metalcomposites.

[0018] A thermal interface material (TIM) may be placed between the dieand the heat spreader cavity interfaces. A TIM can be a solder, apolymer/solder composite, or a polymer.

[0019] A sealant may be employed to affix heat spreader 300 to otherobjects, such as package components, including a substrate (not shown).In exemplary implementations, silicone- or epoxy-based sealants may beemployed.

[0020] Sealant flows over each step 320 to form a mechanical link.Sealant flow 370 is identified in FIG. 3B. In various embodiments,thickness of sealant at the heat spreader surface ranges from 1.5 mm to3 mm, and extended lips 310 are 2 mm wide.

[0021] According to embodiments of the present invention, an extensionto lip 310, such as step 320, increases the surface area of each lip 310of heat spreader 300. Thus, sealant coverage over heat spreader 300increases, and the sealant may better grip heat spreader 300. Morespecifically, shear stress is distributed above and below lips 310,providing greater area in which to absorb and dissipate stresses. Thestrength of the sealant in the areas of mechanical linkage, coupled withthe adhesive bonding energy, increases the bonding strength and mayprevent failure due to shear stresses at the heat spreader-to-sealantinterface.

[0022] In sum, embodiments of the present invention, which includemechanical links at the heat spreader-to-sealant interface, increaseadhesion of the sealant to the heat spreader and to a package component,such as a substrate. As such, a sealant is more likely to fail at thesubstrate interface or cohesively within the sealant than to failadhesively at the head spreader bonding surface.

[0023]FIGS. 4A and 4B are plan and side views, respectively, of anintegrated heat spreader 400 according to an embodiment of the presentinvention. Heat spreader 400 includes a heat spreader element 401 andlips 410 extending therefrom. A step 420 extends from each lip 410. Asshown in FIG. 4A, each step 420 includes holes 430. Holes 430 maycomprise, for example, circular holes or slots. Sealant may flow througheach hole 430 and over each step 420, forming a mechanical link. Sealant470 is depicted in FIG. 4B.

[0024]FIGS. 5A and 5B are plan and side views, respectively, of anintegrated heat spreader 500 according to an embodiment of the presentinvention. Heat spreader 500 includes heat spreader element 501. Lips510 extend from heat spreader element 501. A step 520 extends from eachlip 510. Each step 520 includes cutouts 540. In some embodiments, edgesof cutouts 540 may be rounded. Sealant may flow through cutouts 540 andup over step 520 to form a mechanical link. Sealant 570 is shown in FIG.5B.

[0025]FIGS. 6A and 6B are plan and side views, respectively, of anintegrated heat spreader 600 according to an embodiment of the presentinvention. Heat spreader 600 includes an integrated heat spreaderelement 601. Lips 610 extend from heat spreader element 601. Each lip610 includes a channel 650, which may be concave. During the process ofattaching heat spreader 600 to a substrate or other component, sealantmay flow into channel 650 to form a mechanical link. Deeper and sharperchannels may achieve greater reductions in delamination, increasing theability of the sealant to adhere to heat spreader 600 under higherstresses. One or more channels of the same or different dimension can beutilized.

[0026] The integrated heat spreader structures described above may befabricated in various ways. For instance, extensions, holes, slots,cutouts, and channels may be stamped during a stamping operationassociated with an integrated heat spreader. Alternatively, structuresmay be formed by grinding or laser etching after a stamping operationassociated with an integrated heat spreader.

[0027] The foregoing description of the preferred embodiments isprovided to enable any person skilled in the art to make or use thepresent invention. Various modifications to these embodiments arepossible, and the generic principles presented herein may be applied toother embodiments as well. As such, the present invention is notintended to be limited to the embodiments shown above but rather is tobe accorded the widest scope consistent with the principles and novelfeatures disclosed in any fashion herein. In particular, variations andcombinations of embodiments presented above may be incorporated intointegrated heat spreaders. For instance, cutouts may be irregularlyspaced, and a step or lip may have a channel, multiple channels, ornotch in a lateral face.

1-17. (Canceled)
 18. An integrated heat spreader constructed andarranged to be adhesively affixed, with a sealant, to at least a portionof a component, the sealant to act as an adhesive interface between theintegrated heat spreader and the component, comprising: a body portion;and a lip portion vertically oriented relative to the body portion, thelip portion being constructed and arranged to define a channel in a facethereof.
 19. The integrated heat spreader of claim 18, wherein thechannel is substantially concave. 20-23. (Canceled)
 24. A method ofmaking an integrated heat spreader, comprising: forming a body portion;and forming a lip portion vertically oriented relative to the bodyportion, wherein the lip portion defines a channel in a face thereof.25. The method of claim 24, wherein the channel is substantiallyconcave.